And Norway surged from 4th place in last year's assessment all the way to the top spot, even though oil prices are down, the World Happiness Report 2017 said.

World Bulletin / News Desk

A bit of cold isn't keeping Norway from basking in the warmth of being the world's happiest country, a UN report out Monday found.

The top four also included Nordic neighbors neighbors Denmark and Iceland as well as Switzerland.

"All of the top four countries rank highly on all the main factors found to support happiness: caring, freedom, generosity, honesty, health, income and good governance," the summary explained.

Rounding out the top ten were Finland (5th), the Netherlands (6), Canada (7), New Zealand (8), and Australia and Sweden tied for 9th.

The entire top ten were wealthier developed nations. Yet money is not the only ingredient in the recipe for happiness, the report said.

In fact, among the wealthier countries the differences in happiness levels had a lot to do with "differences in mental health, physical health and personal relationships: the biggest single source of misery is mental illness," the report said.

"Income differences matter more in poorer countries, but even their mental illness is a major source of misery," it added.

Another major country, China, has made major economic strides in recent years. But its people are not happier than 25 years ago, it found.

The United States meanwhile slipped to the number 14 spot due to less social support and greater corruption; those very factors play into why Nordic countries fare better on this scale of smiles.